Image processing method and apparatus, and recording medium used therewith

ABSTRACT

An image processing method matches the gradations of a first output unit and a second output unit which have different gradation-reproduction ranges. The image processing method sets first-output-unit information on the first output unit, sets output-medium information for use in the second output unit, and finds an output-gradation reproduction curve from the first-output-unit information and the output-medium information.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image processing method andapparatus that perform gradation matching between images formed by afirst output unit and a second output unit which have differentgradation reproduction ranges, and a recording medium used therewith.

2. Description of the Related Art

Conventionally, when a computer system, or the like, uses a printer toprint an image displayed on a monitor, control of the lightness of anoutput image is performed using settings concerning lightness or anoutput gamma value in a printer driver. The printer driver correctsimage data by using a gradation correction curve in accordance with setlightness or the output gamma value.

However, settings for the monitor cannot be reflected when the gradationcorrection curve for the printer is set. Also, the gradation correctioncurve for the printer is set without considering the relationshipbetween a gradation correction curve outputable by the monitor and agradation correction curve outputable by the printer.

Accordingly, these cause problems in that an image output by the printeris too bright or too dark than an image displayed on the monitor and inthat part of the output image is too bright to be visible, or part ofthe output image is too dark for the gradation of the part to beperceptible.

In addition, conventionally, when the computer, or the like, uses theprinter to print the image displayed on the monitor, control of thelightness or contrast of the image output by the printer is performed bychanging lightness and contrast values in settings for the printerdriver. The printer driver controls output lightness and contrast byusing the set values to calculate the gradation correction curve, andcorrecting image data.

In the above conventional cases, regardless of gradation characteristicsreproduced by the monitor, a gradation curve for output is set andoutput by lightness-change processing such as entirely brightening ordarkening, or performing contrast-change processing such as increasingor reducing the inclination of the gradation curve.

Accordingly, this causes problems in that an image output by the printeris too bright or too dark,. and in that too dark portions, too brightportions, etc., appear.

SUMMARY OF THE INVENTION

Accordingly, to solve the foregoing problems, it is an object of thepresent invention to provide an image processing method and apparatusfor matching the gradation of images output by different output units,and a recording medium used therewith.

It is another object of the present invention to provide an imageprocessing method and apparatus that can preferably output images, evenif lightness or contrast is controlled, and a recording medium usedtherewith.

It is a further object of the present invention to provide an imageprocessing method and apparatus that can provide a preferably outputimage in accordance with a change in reproduction characteristics of anoutput apparatus, and a recording medium used therewith.

To these ends, according to an aspect of the present invention, there isprovided an image processing method for performing gradation matchingbetween images formed by a first output unit and a second output unitwhich have different gradation-reproduction ranges. The image processingmethod includes the steps of setting first-output-unit information onthe first-output unit, setting output-medium information for use in thesecond output unit, and finding an output-gradation reproduction curvefrom the first-output-unit information and the output-mediuminformation.

According to another aspect of the present invention, there is providedan image processing method for performing gradation matching betweenimages formed by a first output unit and a second output unit which havedifferent gradation-reproduction ranges, wherein a lightness changingprocess by the second output unit is operatively associated with thegradation-reproduction range of the second output unit, and a contrastchanging process by the second output unit is operatively associatedwith the gradation-characteristic curve of the first output unit.

According to another aspect of the present invention, there is providedan image processing method for performing gradation matching betweenimages formed by a first output unit and a second output unit which havedifferent gradation-reproduction ranges. The image processing methodincludes the steps of controlling the first output unit to output agradation image in accordance with image data representing gradation,controlling the second output unit to output a plurality of gradationimages corresponding to the results of different gradation processes onthe image data representing gradation, inputting information for, fromamong the plurality of gradation images output from the second outputunit, selecting a gradation image corresponding to the gradation imageoutput from the first output unit, and setting gradation conversionconditions for the second output unit by using the selected gradationimage as a target.

According to another aspect of the present invention, there is providedan image processing apparatus for performing gradation matching betweenimages formed by a first output unit and a second output unit which havedifferent gradation-reproduction ranges. The image processing apparatusincludes a setting unit for setting first-output-unit information on thefirst output unit, a setting unit for setting output-medium informationfor use in the second output unit, and a finding unit for finding anoutput-gradation reproduction curve from the first-output-unitinformation and the output-medium information.

According to another aspect of the present invention, there is providedan image processing apparatus for performing gradation matching betweenimages formed by a first output unit and a second output unit which havedifferent gradation-reproduction ranges. The image processing apparatusincludes an associating unit for operatively associating a lightnesschanging process performed by the second output unit with thegradation-reproduction range of the second output unit, and anassociating unit for operatively associating a contrast changing processperformed by the second output unit with the gradation-characteristiccurve of the first output unit.

According to another aspect of the present invention, there is providedan image processing apparatus for performing gradation matching betweenimages formed by a first output unit and a second output unit which havedifferent gradation-reproduction ranges. The image processing apparatusincludes a control unit for controlling the first output unit to outputa gradation image in accordance with image data representing gradation,a control unit for controlling the second output unit to output aplurality of gradation images corresponding to the results of differentgradation processes on the image data representing gradation, an inputunit for inputting information for, from among the plurality ofgradation images output from the second output unit, selecting agradation image corresponding to the gradation image output from thefirst output unit, and a setting unit for setting gradation conversionconditions for the second output unit by using the selected gradationimage as a target.

According to a further aspect of the present invention, there isprovided a recording medium containing a program for implementing animage processing method for performing gradation matching between imagesformed by a first output unit and a second output unit which havedifferent gradation-reproduction ranges, wherein the program includesthe steps of setting first-output-unit information on the first outputunit, setting output-medium information for use in the second outputunit, and finding an output-gradation reproduction curve from thefirst-output-unit information and the output-medium information.

According to a further aspect of the present invention, there isprovided a recording medium containing a program for implementing animage processing method for performing gradation matching between imagesformed by a first output unit and a second output unit which havedifferent gradation-reproduction ranges, wherein the program includesthe steps of operatively associating a lightness changing processperformed by the second output unit with the gradation-reproductionrange of the second output unit, and operatively associating a contrastchanging process performed by the second output unit with thegradation-characteristic curve of the first output unit.

According to a further aspect of the present invention, there isprovided a recording medium containing a program for implementing animage processing method for performing gradation matching between imagesformed by a first output unit and a second output unit which havedifferent gradation-reproduction ranges, wherein the program includesthe steps of controlling the first output unit to output a gradationimage in accordance with image data representing gradation, controllingthe second output unit to output a plurality of gradation imagescorresponding to the results of different gradation processes on theimage data representing gradation, inputting information for, from amongthe plurality of gradation images output from the second output unit,selecting a gradation image corresponding to the gradation image outputfrom the first output unit, and setting gradation conversion conditionsfor the second output unit by using the selected gradation image as atarget.

Further objects, features and advantages of the present invention willbecome apparent from the following description of the preferredembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an image processing apparatusaccording to a first embodiment of the present invention;

FIG. 2 is a graph showing an example of printing gradationcharacteristics;

FIG. 3 is a graph showing an example of display gradationcharacteristics;

FIG. 4 is a graph showing gradation characteristics obtained whenlightness compression is performed;

FIG. 5 is a flowchart illustrating an image output process;

FIG. 6 is a drawing showing an example of a user interface for settingimage-output conditions;

FIG. 7 is a flowchart illustrating a process for setting image-outputconditions;

FIG. 8 is a block diagram showing an image processing apparatusaccording to a second embodiment of the present invention;

FIG. 9 is a block diagram showing an image processing apparatusaccording to a third embodiment of the present invention;

FIG. 10 is a graph showing lightness-corrected gradationcharacteristics;

FIG. 11 is a graph showing contrast-corrected gradation characteristics;

FIG. 12 is a flowchart illustrating a process for setting image-outputconditions on a third embodiment of the present invention;

FIG. 13 is a drawing showing an example of a user interface for settinglightness and contrast;

FIG. 14 is a block diagram showing an image processing apparatusaccording to a fourth embodiment of the present invention;

FIG. 15 is a flowchart illustrating a process for setting image-outputconditions on a fourth embodiment of the present invention;

FIG. 16 is a drawing showing an example of a test pattern; and

FIG. 17 is a drawing showing examples of printed test patterns.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the accompanying drawings, embodiments of the presentinvention are described below.

First Embodiment

FIG. 1 is a block diagram showing an image processing apparatusaccording to a first embodiment of the present invention. This imageprocessing apparatus includes an image memory 10 for storing image data,a monitor 11 for displaying an image, a gamma setting unit 12 forsetting display characteristics, a video signal generating unit 13 forusing a set gamma value to convert the image data into a video signal, aprinter 14 for printing an image, a paper setting unit 15 for setting aprinting paper type, a gradation conversion unit 16 for performinggradation matching between the image displayed on the monitor 11 and theimage printed by the printer 14, a color matching processing unit 17 forperforming color matching between the image displayed on the monitor 11and the image printed by the printer 14, and an output image processingunit 18 for converting the image data into a printer driving signal.

The image data specifically includes data digitized by a device such asa digital camera or a scanner and data generated by computer graphics.The image data is stored, as pixel levels corresponding to lightness, inthe image memory 10. Each pixel level is represented by the 8-bit valuesof red (R), green (G), and blue (B). Value 255 represents a maximumlightness and value 0 represents a minimum lightness.

The monitor 11 is a display such as a cathode-ray tube or a liquidcrystal display. In the monitor 11, with respect to the intensity V of adriving signal, luminance signal Y has a substantial relationship asexpressed by the following expression (1):Y=V^(γ) ^(monitor)   (1)

The video signal generating unit 13 uses a digital-to-analog converter(DAC) to generate video driving signal V corresponding to pixel level I.Assuming that the input/output characteristics of the DAC are given bythe following expression (2):V=(I/255)^(1/γ) ^(video)   (2)luminance value Y displayed on the monitor 11 and pixel level I has arelationship as expressed by the following expression (3):V=(I/255)^(γ) ^(monitor) ^(/γ) ^(video) =(I/255)^(γ)  (3)

In the first embodiment, the input/output characteristics of the DAC ofthe video signal generating unit 13 are controlled so that therelationship between luminance value Y displayed on the monitor 11 andpixel level I is represented by gamma value γ.

The printer 14 is an ink-jet type in which, by discharging and fixingdroplets of cyan (C), magenta (M), yellow (Y), and black (K) inks onprinting paper, the gradation of each is indicated by the density of thedroplets.

In accordance with input RGB pixel levels, the. output image processingunit 18 generates data for controlling discharge of C, M, Y, and K inksin order to reproduce desired color on the paper.

In the printer 14, a type of paper can be selected from among papertypes such as plain paper, coated paper, and glossy paper, and the typeof paper can be designated by the paper setting unit 15.

The gradation conversion unit 16 performs gradation conversion inaccordance with gamma value setting and settings on the paper so as toperform gradation matching on the image displayed on the monitor 11.

A method of setting gradation conversion conditions for use in thegradation conversion unit 16 is described below.

The relationship between pixel levels and output color can be found bythe following procedure. Without performing gradation conversion, graypatches obtained by changing pixel level (R, G, B) from (0, 0, 0) to(255, 255, 255) are output onto a type of paper. The color of each graypatch is measured using a calorimeter, and relative reflection factor Ris found, with the paper plane used as a reference (reflection 1).Relative reflection factor R is converted into lightness L* by using thefollowing expression (4):L*=116^(1/3)−16(R>0.008856)L*=903.29R(R≦0.008856)  (4)The relationship between pixel level I and the found lightness L* is therelationship between the pixel level and the output color.

In FIG. 2, an example of a relationship between pixel level I and(printing) lightness L* is shown.

The relationship between pixel level I and lightness L_(m)* is expressedbased on gamma value γ (of the monitor 11) by the following expression(5): $\begin{matrix}\begin{matrix}{L_{m^{*}} = {{116( {Y/{Y0}} )^{1/3}} - {16( {{Y/{Y0}} > 0.008856} )}}} \\{= {{116( {I/255} )^{\gamma/3}} - 16}} \\{L_{m^{*}} = {903.29( {Y/{Y0}} )( {{Y/{Y0}} \leq 0.008856} )}} \\{= {903.29( {I/255} )^{\gamma}}}\end{matrix} & (5)\end{matrix}$In expression (5), YO represents the maximum luminance of the monitor11. L_(m)* represents lightness displayed on the monitor 11. In FIG. 3,the relationship between pixel level I and display lightness L* whichare obtained when γ=2.2 is shown.

From FIGS. 2. and 3, it is understood that the monitor 11 and theprinter 14 has different displayable ranges: the monitor 11 has adisplayable range of lightness from 0 to 100, while the printer 14 has adisplayable range of lightness from 10 to 100.

Accordingly, in order to obtain a printed output which is matched withan image displayed on the monitor 11, lightness must be compressed. Inthe first embodiment, the displayable range of lightness is linearlycompressed into a printable range of lightness. Specifically, theconversion expressed by the following expression (6) is performed:L _(p) *=L _(m)*(L_(max) −L _(min))+L _(min)  (6)where L_(max) represents a maximum printable lightness, L_(min)represents a minimum printable lightness, and L_(p)* represents aprinted lightness.

In FIG. 4, the relationship between lightness L_(p)* obtained bylightness compression and pixel level I is shown.

In order to obtain the output gradation characteristics shown in FIG. 4,the gradation conversion conditions are found in the following manner.

First, concerning sixteen gradations in which the pixel level of each ofR, G, and B is 0, 17, 34, 51, 68, 85, 102, 119, 136, 153, 170, 187, 204,221, 238, and 255, input values for outputting the lightness shown inFIG. 4 are found from FIG. 2.

By way of example, it is found from FIG. 4 that objective lightnesscorresponding to pixel level 17 is 12. Also, FIG. 2 indicates that pixellevel 9 needs to be set for outputting lightness 12. Thus, afterconverting input pixel level 17 into 9, the gradation conversion unit 16needs to output the value 9 converted from the input level 17.

Next, converted values corresponding to pixel levels 0 to 255 are foundfrom the above obtained sixteen gradations by using interpolation.Although the interpolation is linear interpolation, it is preferable touse smooth interpolation such as spline. Also, by setting the precisionof interpolation calculation to eight bits or greater, aninterpolation-caused loss of gradation can be prevented.

This process can create gradation conversion conditions capable ofreproducing the gradation characteristics in FIG. 4. The gradationconversion unit 16 uses the gradation conversion conditions in commonfor RGB color components.

With reference to the flowchart shown in FIG. 5, a process foroutputting an image by the printer 14 is described below.

In step S61, an image is input to the image memory 10.

In step S62, output conditions are set, such as reading and setting ofgamma value γ (for the monitor 11) which is used by gradation matching,and the setting of the paper type in the paper setting unit 15.

In step S63, based on the output conditions set in step S62, thegradation conversion unit 16 performs gradation conversion processingusing the gradation conversion conditions obtained by the aboveinterpolation and expressions (5) and (6).

In step S64, color matching processing is performed by the colormatching processing unit 17, and in step S65, an image output by thecolor matching processing 17 is transferred to the printer 14 by theoutput image processing unit 18.

Next, the setting of the output conditions in step S62 is describedbelow with reference to FIGS. 6 and 7.

FIG. 6 shows an example of a user interface in the printer driver. Whenoutputting an image, the user sets the items of the interface to matchdesired output conditions, and subsequently presses an OK button 77.This completes the setting of the output conditions, and the outputimage can be obtained. The interface contains a printing purpose settingunit 71 for setting an image printing purpose, a paper type setting unit72 for setting a paper type for use in printing, a paper size settingunit 73 for setting the size of paper for use in printing, a colormatching setting unit 74 for setting the determination of whether colormatching processing is performed on an image to be output, acolor-matching-technique setting unit 75 for setting a color matchingtype, an objective gamma setting unit 76 for setting gamma value γ_(p)as a matching target, the OK button 77 for confirming completion of allsettings, and a cancel button 78 for aborting a setting operation.

With reference to the flowchart in FIG. 7, a process for setting theoutput conditions in step S62 (FIG. 5) is described below in which theuser interface in FIG. 6 is used to determine each setting item.

In step S801, the process determines whether the cancel button 78 ispressed. If the cancel button 78 is pressed, the setting of the outputconditions in step S62 is terminated. If the cancel button 78 is notpressed, the process proceeds to step S802.

In step S804, the process determines whether the OK button 77 ispressed. If the OK button 77 is pressed, the process proceeds to stepS81. If the OK button 77 is not pressed, the process goes back to stepS801.

In step S81, by using the printing purpose setting unit 71 toselectively set a printing purpose, printing purpose information isacquired, such as black and white (B/W) document, document/table,photograph, desktop publishing (DTP), graphics, user definition, orother.

In step S82, by using the paper type setting unit 72 to set a papertype, from among a plurality of paper types such as plain paper, coatedpaper, and glossy paper, information on the type of paper is acquired.The gradation conversion condition is set by using the relationshipbetween pixel level I and printing lightness L*, which corresponds tothe acquired information on the type of paper.

In step S83, by using the paper size setting unit 73 to set a papersize, information on a paper size, such as A3, A4, A5, B4, B5, postcard,or other, is acquired.

In step S84, by using the color matching setting unit 74 to switch oncolor matching, ON/OFF information on the color matching processing isacquired.

In step S85, based on the information acquired in step S84, if the colormatching processing has been switched on in step S84, the processproceeds to step S86, or if the color matching processing has not beenswitched on in step S84, the process terminates the output conditionprocess.

In step S86, by using the color-matching-technique setting unit 75 toset a color matching technique, information on a technique, such asperceptual mode, saturation mode, or color difference minimizing mode,is acquired.

In step S87, by using the objective gamma setting unit 76, gamma valueγ_(p) on the monitor 11 for which gradation matching is performed isacquired. Here, the gamma value γ set in the gamma setting unit 12 isset as an initial value in the objective gamma setting unit 76, so thatthe initial value can be changed depending on user's preference. Thegradation conversion condition is set by using the relationship betweenpixel level I and printing lightness L_(m)*, which corresponds to theset gamma value γ.

The above-described process sets the output conditions.

As described above, based on the relationship between pixel level I andprinting lightness L_(m)*, which corresponds to the set gamma value γ,and on the relationship between pixel level I and printing lightness L*,which corresponds to the acquired information on the type of paper, byfinding the relationship between each pixel level and each correctionvalue, printing that is matched with an image displayed on the monitor11 in gradation can be performed. In particular, by linearly compressingthe gradation reproduction range of the monitor 11 and the printingpaper by using lightness that is an equal factor with respect to a humansense of luminous intensity, visually preferable gradation reproductioncan be performed.

In the first embodiment, in the described interpolation of the outputgradation characteristics, conversion values corresponding to pixellevels from 0 to 255 are found from sixteen gradations. However,obviously, the number of gradations is not limited to the sixteengradations, and may be changed to 32 gradations, depending on the memorycapacity and conversion precision required for practice.

In the first embodiment, as described above, the gradation conversionprocess is performed, as the gradation conversion process in thegradation conversion unit 16, such that whenever an image is output, theoutput gradation characteristics are calculated based on expressions (5)and (6) and the interpolation processing. However, the gradationconversion process is not limited thereto. By storing beforehand., in amemory, output gradation characteristics calculated based on typicalcombinations of gamma value γ and paper types, the output gradationcharacteristics may be read from the memory when an image is output.

The user interface shown in FIG. 6. has a form in which selection ismade by the buttons. However, obviously, the user interface shown inFIG. 6 is not limited to the form. Also, a user interface form may beused in which a keyword can be directly input. In other words, the userinterface shown in FIG. 6 may have a form in which output conditionsdesired by the user can be set.

Second Embodiment

A second embodiment of the present invention is a modification of thefirst embodiment. Differences from the first embodiment are describedbelow.

FIG. 8 is a block diagram showing an image processing apparatusaccording to the second embodiment.

The image processing apparatus according to the second embodimentincludes a monitor profile unit 20 and a printer profile unit 21 thatstores output characteristics for each type of paper.

In the monitor profile unit 20, gamma value γ on the monitor 11 and RGBchromaticity of fluorescent material are described. In the printerprofile unit 21, the L_(ab) values and output gradation characteristicsof print colors corresponding to input pixel levels for each type ofpaper are described. General methods for describing these devicecharacteristics include the International Color Consortium (ICC)Profile.

In the image processing apparatus according to the second embodiment,gamma value γ on the monitor 11 is read from the monitor profile unit20, the relationship between the input pixel level and displayedlightness is found, maximum lightness L_(max) and minimum lightnessL_(min) on the presently set paper are read from the printer profileunit 21, and compressed output lightness L* obtained by expression (6)is found. Next, output gradation characteristics are read from theprinter profile unit 21, and the input pixel level is corrected so thatcompressed output lightness L* can be output.

As described above, by reading input and output characteristics from themonitor profile unit 20 and the printer profile unit 21, finding therelationship of the correction value corresponding to each pixel level,and correcting the RGB value of image data, printing that isautomatically matched in gradation with an image displayed on themonitor 11 can be performed when the monitor 11 and settings on paperare changed.

Third Embodiment

A third embodiment of the present invention is a modification of thesecond embodiment. Differences from the second embodiment are describedbelow.

FIG. 9 is a block diagram showing an image processing apparatusaccording to the third embodiment.

The image processing apparatus according to the third embodimentincludes a brightness setting unit 19 that sets the lightness of anoutput image, and a contrast setting unit 22 that controls the contrastof the output image.

A method for controlling lightness and contrast is described below.

A lightness correction value that is set by the brightness setting unit19 is represented by ΔL. When the set lightness correction value isgreater than a standard, ΔL is positive, while when the set lightnesscorrection value is less than the standard, ΔL is negative. A contrastcorrection value that is set by the contrast setting unit 22 isrepresented by Δγ. When the set contrast correction value is greaterthan a standard, Δγ is positive, while when the set contrast correctionvalue is less than the standard, Δγ is negative.

Lightness correction is performed by changing the values of L_(max) andL_(min) in expression (6). When ΔL is positive, the lightness correctionis expressed by the following expression (7) in which L_(min) inexpression (6) is replaced by L_(min)+ΔL.L _(p) *=L _(m)*(L _(max) −L _(min) −ΔL)+L _(min) +ΔL  (7)When ΔL is negative, the lightness correction is expressed by thefollowing expression (8) in which L_(max) in expression (6) is replacedby L_(max)+ΔL.L _(p) *=L _(m)*(L _(max) +ΔL−L _(min))+L _(min)  (8)

FIG. 10 shows the relationship between pixel level I and lightnessL_(p)* which are obtained when the contrast is corrected. In FIG. 10,concerning lightness L_(p)*, reference numerals 100, 101, and 102 denotea standard state, a brighter state, and a darker state, respectively.

The contrast correction is performed by increasing or reducing gammavalue γ in expression (5). In other words, the relationship between(input) pixel level I and lightness L_(m)* of the contrast-correctedimage is expressed by the following expression (9) in which γ inexpression (5) is replaced by γ+ΔL.L _(m)*=116(I/255)^((γ+Δγ)/3)−16((I/255)^((γ+Δγ))>0.008856)L _(m)*=903.29(I/255)^((γ+Δγ))((I/255)^((γ+Δγ))>0.008856)  (9)

FIG. 11 shows the relationship between pixel level I and lightness L*which are obtained when lightness is changed. Reference numerals 101,111, and 112 denote a standard state, a high contrast state, and a lowcontrast state, respectively.

In the third embodiment, in accordance with gamma value γ on the monitor11 for which gradation matching is performed, which is read from themonitor profile unit 20, the paper type set in the paper setting unit15, the lightness of the output image which is set in the brightnesssetting unit 19, and the contrast of the output image which is set inthe contrast setting unit 22, the gradation conversion conditions arefound by using expressions (7), (8), and (9), and the aboveinterpolation.

With reference to FIGS. 12 and 13, a process for setting each item bythe user interface in the setting of the output conditions is describedbelow.

FIG. 13 shows a form of a printer driver's user interface for settingthe lightness and contrast of the output image. In the flowchart in FIG.12, by using identical reference numerals to denote steps identical tothose described in the first embodiment, a description of the steps isomitted.

In step S87, by using an objective gamma setting unit 86 to performgamma value setting, gamma value γ_(p) on the monitor 11 for gradationmatching is performed is acquired. Here, by setting the gamma value γset in the monitor profile 20, as an initial value in the objectivegamma setting unit 86, the initial value can be changed depending onuser's preference.

In step S88, in a brightness setting unit 89, the user uses a slider barto the lightness of the output image. The positional difference of theset position from the standard position is acquired, which correspondsto the above ΔL. In step S89, in a contrast setting unit 90, the useruses a slider bar to set the contrast of the output image. Thepositional difference of the set position from the standard position isacquired, which corresponds to the above Δγ. After that, the process forsetting the output conditions ends.

As described above, by correcting the RGB values of image data afterfinding the relationship of correction values with respect to pixellevels by associating control of contrast with an increase or decreasein the gamma value of the monitor 11, associating control of lightnesswith the maximum or minimum lightness of the printer 14, the lightnessand contrast of a printing output can be controlled without losing thegradation of an image displayed on the monitor 11. In particular, byperforming gradation correction using lightness that is an equal factorwith respect to a human sense of luminous intensity, gradationcorrection close to a visual sense can be performed.

Fourth Embodiment

A fourth embodiment of the present invention is a modification of thethird embodiment. Differences from the third embodiment are describedbelow.

FIG. 14 is a block diagram showing an image processing apparatusaccording to the fourth embodiment. This image processing apparatusincludes a test pattern generating unit 19 that generates image patternsfor gamma-value test.

Gamma value γ in expression (3) changes depending on the characteristicsof the monitor 11 and the video signal generating unit 13. Ordinarily,in an inexpensive system such as a personal computer system, thecharacteristics of a monitor and a video signal generating unit areunknown, or device differences appear even if the characteristics areknown. Also, depending on an illumination condition in an environment inwhich the monitor 11 is viewed, a perceptible lightness changes.

In order to know display characteristics in an environment of use by theuser, the image processing apparatus according to the fourth embodimentuses the following method to print several types of test patterns, andcompares a displayed test pattern and the printed test patterns. Basedon the results of comparison, the gamma value γ (denoted by referencenumeral 76 in FIG. 6) of the monitor 11 for which gradation matching isperformed is set.

When the gamma value γ of the monitor 11 is set, a gradation example(gradation patch pattern) is generated and stored in the image memory 10by the test pattern generating unit 19. FIG. 16 shows a gradationpattern 161 (as an example of the gradation pattern) and a button 162for going back to the screen for setting the output conditions, whichare displayed on the screen 160 of the monitor 11.

Next, the printer 14 prints a test pattern. The gradation conversionunit 16 uses several gamma values γ to convert the generated gradation,performs the color matching process and the output image process, anduses the printer 14 to print the obtained image. FIG. 17 shows gradationpatterns (as test patterns) 171, 172, 173, 174, 175, and 176 printed onprinting paper 170. The gradations of the patterns 171, 172, 173, 174,175, and 176 are corrected by gamma values γ_(p) of 1.4, 1.6, 1.8, 2.0,2.2, and 2.4, respectively.

With reference to the flowchart shown in FIG. 15, a process for settingeach item in the user interface is described below. By using identicalreference numerals to denote steps identical to those described in thefirst embodiment, a description of the steps is omitted.

In step S801, the process determines whether the cancel button 79 ispressed. If the cancel button 79 is pressed, the process ends. If thebutton 79 is not pressed, the process proceeds to step S802.

In step S802, the process determines whether the button 76 is pressed.If the button 76 is pressed, the process proceeds to step S803. If thebutton 76 is not pressed, the process proceeds to step S804.

In step S803, the gradation image shown in FIG. 16 is displayed on themonitor 11, and the image shown in FIG. 17 is output from the printer14. By pressing the “GO BACK TO SETTING SCREEN” button 162 in FIG. 16,the process proceeds to step S804.

In step S804, the process determines whether the OK button 78 ispressed. If the OK button 78 is pressed, the process proceeds to stepS81. If the OK button 78 is not pressed, the process goes back to stepS801.

According to the fourth embodiment, preferable gradation matching can beperformed regardless of device difference and an illumination condition.

Other Embodiments

The present invention may be applied to a system composed of a pluralityof apparatuses such as a host computer, an interface apparatus, areader, and a printer) and to a single apparatus such as a facsimilemachine or a facsimile machine.

Obviously, the objects of the present invention can be achieved byproviding a system or apparatus with a recording medium containing theprogram code of software for implementing the functions of the foregoingembodiments, and controlling the computer (or a central processing unitor a microprocessor unit) of the system or apparatus to read and executethe program code from the recording medium.

In this case, the program code read from the recording medium implementsthe functions of the foregoing embodiments, so that the recording mediumcontaining the program code constitutes the present invention.

For example, a floppy disk, a hard disk, an optical disk, amagneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatilememory, a ROM, etc., can be used as the recording medium for providingthe program code.

In addition, by executing the program code read by the computer, thefunctions of the foregoing embodiments are implemented. Obviously, thisalso includes a case in which based on the instructions of the programcode, an operating system activated on the computer performs part ofactual processing, and the processing implements the functions of theforegoing embodiments.

Moreover, the present invention includes a case in which after theprogram code read from the recording medium is written in a memoryprovided in an add-in board inserted into the computer or in an add-inunit connected to the computer, a CPU, or the like, which is provided inthe add-in board or unit performs, based on the instructions of theprogram code, all or some of actual processes, and the processingimplements the functions of the foregoing embodiments.

While the present invention has been described with reference to whatare presently considered to be the preferred embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments. On the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. The scope of the following claims is to beaccorded the broadest interpretation so as to encompass all suchmodifications and equivalent structures and functions.

1. An image processing method for performing gradation matching betweenimages formed by a first output unit and a second output unit which havedifferent gradation-reproduction ranges, said image processing methodcomprising the steps of: setting first-output-unit information on saidfirst output unit; setting output-medium information for use in saidsecond output unit; and finding an output-gradation reproduction curvefrom the first-output-unit information and the output-mediuminformation.
 2. An image processing method according to claim 1, whereinsaid first output unit is a monitor.
 3. An image processing methodaccording to claim 1, wherein the first-output-unit information is agradation characteristic of a monitor.
 4. An image processing methodaccording to claim 3, wherein the first-output-unit information is setby a user.
 5. An image processing method according to claim 3, whereinthe first-output-unit information is set by reading predetermined data.6. An image processing method according to claim 1, wherein said secondoutput unit is a printer.
 7. An image processing method according toclaim 1, wherein the output-medium information for use in said secondoutput unit is a paper type.
 8. An image processing method according toclaim 7, where the output-medium information for use in said secondoutput unit is set by a user.
 9. An image processing method forperforming gradation matching between images formed by a first outputunit and a second output unit which have differentgradation-reproduction ranges, wherein a lightness changing process bysaid second output unit is operatively associated with thegradation-reproduction range of said second output unit, and a contrastchanging process by said second output unit is operatively associatedwith the gradation-characteristic curve of said first output unit. 10.An image processing method according to claim 9, wherein said firstoutput unit is a monitor.
 11. An image processing method according toclaim 10, wherein said second output unit is a printer.
 12. An imageprocessing method according to claim 9, wherein thegradation-characteristic curve of said second output unit is set basedon the gradation-reproduction range of said second output unit and thegradation-characteristic curve of said first output unit. 13-15.(canceled)
 16. An image processing apparatus for performing gradationmatching between images formed by a first output unit and a secondoutput unit which have different gradation-reproduction ranges, saidimage processing apparatus comprising: means for settingfirst-output-unit information on said first output unit; means forsetting output-medium information for use in said second output unit;and means for finding an output-gradation reproduction curve from thefirst-output-unit information and the output-medium information.
 17. Animage processing apparatus for performing gradation matching betweenimages formed by a first output unit and a second output unit which havedifferent gradation-reproduction ranges, said image processing apparatuscomprising: means for operatively associating a lightness changingprocess performed by said second output unit with thegradation-reproduction range of said second output unit; and means foroperatively associating a contrast changing process performed by saidsecond output unit with the gradation-characteristic curve of said firstoutput unit.
 18. (canceled)
 19. A recording medium containing a programfor implementing an image processing method for performing gradationmatching between images formed by a first output unit and a secondoutput unit which have different gradation-reproduction ranges, theprogram comprising the steps of: setting first-output-unit informationon said first output unit; setting output-medium information for use insaid second output unit; and finding an output-gradation reproductioncurve from the first-output-unit information and the output-mediuminformation.
 20. A recording medium containing a program forimplementing an image processing method for performing gradationmatching between images formed by a first output unit and a secondoutput unit which have different gradation-reproduction ranges, theprogram comprising the steps of: operatively associating a lightnesschanging process performed by said second output unit with thegradation-reproduction range of said second output unit; and operativelyassociating a contrast changing process performed by said second outputunit with the gradation-characteristic curve of said first output unit.21. (canceled)